It is well known to utilize high frequency (20 kHz or above) in the operation of fluorescent lamps for the purpose of eliminating standard 60 cycle noise and reducing power loss via lengthy transmissions within a relatively large building complex.
In the most common prior practice, 60 Hz single phase power has been distributed to be rectified at each fixture. In a large building this neccessitates many rectifiers, and large, usually electrolytic, condensers or capacitors and perhaps large inductors. Inductors used for such purposes are inefficient, costly and noisy while electrolytic capacitors are unreliable, temperature sensitive and have limited lifetimes. Capacitor filters used alone lead to a very low power factor for the system and consequently to large power transmission losses.
Prior proposed systems to obtain the benefit of high frequency operation of the lamps by rectifying AC to provide DC to high frequency inverters and to operate at the necessary high power factor, high efficiency and low noise have either been prohibitively costly or have made unacceptable compromises in performance and reliability. No one has succeeded in providing a system which has found acceptance in the market place, which has been affordable and has, the advantages of the present, safe, economic, reliable, efficient and flexible system and ballast for operating at frequencies in the range of about 20 to 30 kHz of higher.
The present invention satisfies this long felt need.